Apparatus for applying a coating on printing cylinder



' July 7,1970 A. B. POSCHEL 1 ,9

APPARATUS FOR APPLYING A COATING ON PRINTING CYLINDER Filed March 18. 1969 INVENTOR ALFRED a. POSCHEL Arron/V5 Y5 United States Patent 3,518,965 APPARATUS FOR APPLYING A COATING ON PRINTING CYLINDER Alfred B. Poschel, 1220 N. State St., Chicago, Ill. 60610 Filed Mar. 18, 1969, Ser. No. 808,200 Int. Cl. Bc 11/02 US. Cl. 118--106 6 Claims ABSTRACT OF THE DISCLOSURE An apparatus for applying a coating on a rotating cylinder including an elastic blanket having a series of minute protrusions on one face thereof, the face of the blanket being positioned to contact the surface of the cylinder, means for moving the blanket in a direction along the axis of the cylinder, and means for providing a flow of liquid onto the cylinder adjacent the blanket such that the blanket spreads and smooths the liquid on the cylinder as a smooth even coating.

In the production of gravure printing cylinders a common method of operation, known as the direct method, requires the provision of a copper plated cylinder with a continuous and perfectly even and smooth light sensitive coating.

In such direct method, a design is first copied on the light sensitive coating of the cylinder by means of a film positive which is brought in close contact with the cylinder while under a suitable light exposure. The action of the light insolubilizes the exposed areas of the design which, after suitable development, form an acid resisting stencil on the cylinder. The prepared cylinder is then etched with iron chloride solutions until the required depth of the design is produced in the design areas not covered and protected by a coating stencil. After removal of the stencil and final finishing the etched cylinder can then be used for gravure printing.

It will be appreciated that the physical condition of the applied light sensitive coating is of the utmost importance in obtaining satisfactory results. And, the quality or success of the various steps of such direct method in producing gravure printing cylinders and/or plates de pends on the physical condition of the applied coating. There are presently two different methods employed in applying the light sensitive coating to the copper plated cylinders. The method most commonly used consists of applying the light sensitive coating solution by spray coating. This is accomplished by providing a spraygun which is arranged to move along the periphery of the cylinder while the cylinder is rotating, until the cylinder is ap propriately covered with coating.

Some light-sensitive coatings are not suitable for spray coating. Accordingly, the second method in use consists of applying the light sensitive coating by means of rollers. In this latter method a movable rubber roller in contact with the cylinder distributes a proper amount of coating on the cylinder.

The foregoing methods of applying the light sensitive coating generally give satisfactory results if sufiicient care is exercised, but nevertheless they have inherent deficiencies which may cause flaws and failures.

In spray coating one of the difficulties is that a critical adjustment of the air pressure and the liquid supply is needed to obtain a uniform and smooth coating on the cylinder, and to avoid excessive variations of the coating thickness on each cylinder and on successive cylinders.

In roller coating one of the difficulties is that of keeping the rubber roller free of any dust particles, which tend to be transferred and embedded in the coating.

Accordingly, the present invention discloses a new and improved apparatus for coating cylinders. It is described in the following disclosure and is further explained by the attached drawings:

FIG. 1 is a perspective view of the coating apparatus according to my invention showing the apparatus mounted adjacent a rotatable cylinder;

FIG. 2 is a perspective view of a coating blanket or sheet in accordance with my invention;

FIG. 3 is a perspective view of the sheet of FIG. 2 positioned in mounting bars;

FIG. 4 is a side view of the sheet of FIGS. 2 and 3 arranged to be placed in operating position;

FIG. 5 is a side view of the sheet of FIGS. 2, 3 and 4 placed in operating position as shown in FIG. 1; and

FIG. 6 is an enlarged section of the front on cylinder facing side of the blanket, of my invention.

My new apparatus 11 includes an elastic blanket or sheet 13, a curved mounting body 15, a coating container 17 and an adjustable holder arm 19 which positions the apparatus 11 relative to the associated rotatable cylinder 22. The elastic or flexible sheet 13, shown separately in FIG. 2, is an important functional part of the new coating device. It may consist of solvent resisting synthetic rubber or of other suitable material like polyethylene, which can be molded or cast and which has elastic and flexible properties. The front or cylinder facing side 21 of the elastic sheet has a special construction as more clearly shown in FIG. 6, and as will now be explained.

Facing side or face 21 presents a multitude of minute protrusions or cones 23 which are evenly spaced and are all of identical height. These minute cones 23 constitute the actual working surface of the sheet 13. The back, or nonfunctioning, face 25 of sheet 13 may be smooth.

If one embodiment, the diameter of the top of the cone 23 is about .002", the spacing between cone centers is about .008", and the height of the protruding cone is about .003". The dimensions of the cones can be varied to suit the viscosity of the coating of the coating solution and to obtain the desired thickness of the final coating, which, can be determined empirically.

The purpose of the minute protruding cones 23 on the blanket or sheet 13 is to permit the free but measured flow of the applied coating solution on the surface of the rotating cylinder 22.

In operation, the coating apparatus 11 is first connected to the mechanical drive. Next, the apparatus 11 is moved against the cylinder 11 and so that the elastic blanket 13 folds itself about two inches around the curved surface of the cylinder 22, see FIG. 5..

The narrow interstices in the coating, caused by the brushing action of the cones while they are in contact with the surface of the rotating cylinder, will be bridged by the leveling flow of the coating as soon as the coating device moves on sidewards and leaves the zone of its coating application, as .will be explained hereinafter.

The multitude of the minute cones while in contact with the surface of the rotating cylinder acts also like a filter retaining dust particles from being carried into the coating.

In one embodiment, the curved body is made from 6 diameter tubing cut in half and is 4" in Width. These dimensions are, of course, changeable. Any materials such as aluminum, stainless steel, or plastics could be used as the body material of body 15.

FIG. 3 shows the means or apparatus for holding the blanket 13 in position. Both ends of the coating blanket are held or clamped between small holder bars 27 and 29.

As ShOiWl'l in FIG. 4, one end (the top end as oriented in the figures) of the blanket 13 is first affixed directly to the top and the open end of the curved 'body 15. Next,

the other end of the blanket is pulled over the open side of the curved body 15, and is then secured by means of bars and suitable means such as screws to the back of a shoulder bar 31 which is fixed to the lower-front side of the body 15. The screws serve to pull the blanket as tightly as needed.

Referring now to FIG. 5 as [well as FIG. 1, the container 17 containing the coating fluid is supported by an extension arm 35 fixed to the top of the curved body 15 on its upper front side. Arm 35 is bent at an angle and the forward part of the arm reaches about two inches over the front top edge of the curved body 15. Arm 15 is arranged so that it does not interfere with the bars and holding of the coating blanket 13. The forward part 35A of arm 35 is angled with respect to the vertical and this forward part of the arm has an aperture for receiving the neck of the coating container 17. The forward part 35A of arm 35 has a collar 37 afiixed thereto to hold the container 17 securely in place by means of suitable screws and to permit easy removal of the container for refilling or cleaning.

The coating container 17 is a small vessel holding coating liquid to be coated on the cylinder and its bottom end has a tube-like opening with a suitable valve indicated schematically at 39.

Referring to FIG. 1, in operation the apparatus 11 is arranged to move toward the right as the cylinder 22 rotates clockwise.

The coating solution is arranged to flow from the container 17 onto the cylinder 22 ahead, in front of, the coating blanket 13. The valve controls the rate of flow of the liquid. The rate of flow of liquid is adjusted dependent on the circumference of the cylinder and the speed at which the coating apparatus 11 is caused to move longitudinally along the cylinder.

The supporting arm 19 is connected by a ball joint 41 to a short piece 43 which screws and fits on the curved body 15. The ball joint 41 permits the adjustment of the angle at which the coating apparatus fits against the cylinder 22. In operation the apparatus 11 is inclined slightly towards the direction of the movement so that a surplus of coating will flow off on the leading edge instead of overflowing the opposite edge of the coating blanket, which would spoil the coating by leaving a surplus on the cylinder.

It will be understood that this new coating device is adapted to be used with the motorized and speed controlled drive for the spray coating device which is furnished with a standard cylinder photoengraving machine, as shown in my patent application Ser. No. 724,020, filed Apr. 25, 1968, and that this new coating apparatus can, with slight adjustments, also be used with other machines of the similar type.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true sprit and scope of the invention.

I claim:

1. An apparatus for applying a coating on a rotating cylinder comprising, in combination, an elastic blanket having a series of minute protrusions on one face thereof; said one face of said blanket being positioned to contact the surface of said cylinder, means for moving said blanket in a direction along the axis of said cylinder; and means for providing a flow of liquid onto said cylinder adjacent said blanket such that said blanket spreads and smooths said liquid on said cylinder as a smooth even coating.

2. An apparatus as in claim 1 wherein said blanket comprises a rectangular sheet, and wherein the longitudinal axis of said sheet is included at an angle as said sheet is moved along the axis of said cylinder.

3. An apparatus as in claim 1 wherein said means for providing a fluid comprises a fluid containing container mounted for movement corresponding to the movement of said blanket.

4. An apparatus as in claim 1 wherein said means for providing a fluid includes a fluid control valve.

5. An apparatus as in claim 1 wherein the protrusions on said blanket comprise a pattern of cones.

6. An apparatus as in claim 1 wherein means are provided for selectively wrapping said blanket partially around said cylinder to effect a controlled spreading of said liquid.

References Cited UNITED STATES PATENTS 2,103,956 12/1937 Schumacher.

2,466,734 4/ 1949 Piazze 118-261 2,766,719 10/1956 Poschel 118107 X 2,866,992 1/ 1959 Toulmin 118-257 X 3,006,317 10/ 196 1 Showalter 118212 3,129,448 4/ 1964 Mittman 15187 X 3,317,644 5/ 1967 Takai.

3,395,034 7/ 1968 Przybilla 1l7-34 WALTER A. SCHEEL, Primary Examiner L G. MACHLIN, Assistant Examiner U.S. Cl. X.R. 

